The present invention relates to a method for producing a (meth)acrylic ester polymer not containing any aromatic compound derived from a solvent and to a composition comprising the polymer. More particularly, the invention relates to the above method for producing a copolymer of a (meth)acrylic ester monomer and a monomer having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond. In the context of the invention, the (meth)acrylic ester means an ester of acrylic acid and/or an ester of methacrylic acid.
The polymer comprising a (meth)acrylic ester monomer unit as a molecular chain and having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond (hereinafter referred to also as polymer (A)) is described in the official gazettes Japanese Kokai Publication Sho-59-078223, Japanese Kokai Publication Sho-59-168014, Japanese Kokai Publication Sho-60-031556, Japanese Kokai Publication Sho-60-228516, Japanese Kokai Publication Sho-60-228517, Japanese Kokai Publication Sho-63-112642, etc., and known to be of use in such applications as sealants and adhesives. The polymer is particularly useful for use in a composition comprising it in combination with an oxyalkylene polymer having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond (hereinafter referred to also as oxyalkylene polymer (B)).
In the production of said polymer (A), aromatic compounds such as toluene and xylene are generally used as polymerization solvents. This is because these are good solvents for the polymer and available at low cost. However, because of environmental needs for paying attention to the sick-house problem, alleviation of the environmental burden within clean-rooms for semiconductor production, etc., it is desirable to employ solvents in lieu of such aromatic compounds.
The object of the present invention is to provide a method for producing a polymer (A) utilizing a solvent which, though not an aromatic compound, can be used for the production of said polymer (A) and a composition comprising the polymer (A) obtainable by said method.
The inventors of the present invention found that by using a certain nonaromatic solvent, namely one or more solvent species selected from the group consisting of alcohol solvents and carbonyl group-containing solvents, preferably one or more members selected from the group consisting of alcohols containing 3 or 4 carbon atoms and dialkyl carbonates, the polymerization reaction of interest can be allowed to proceed in the same way as it is the case with an aromatic solvent and that the resulting polymer does not separate out as a precipitate but remains dissolved in the solvent and further that because of the lower intensity of the so-called solvent odor, said nonaromatic solvent is quite suitable for the production of polymer (A). At the same time, the inventors further discovered that when a certain azo polymerization initiator is used in combination with said nonaromatic solvent in the production of polymer (A), the emission of VOC (Volatile Organic Compound) from the formulation or composition thereof as coated on a substrate can be more effectively suppressed. It was also found by the inventors that compared with the conventional polymer produced by using an aromatic solvent, the polymer (A) produced by the above method of the invention features a narrower molecular weight distribution (Mw/Mn), an improved compatibility with said oxyalkylene polymer (B) to be blended therewith, and an improved weatherability. The inventors further found that because the molecular weight distribution can be narrowed, the viscosity of the composition can also be reduced without detracting from its dynamic properties and weatherability, with the result that the workability in coating with the composition can be improved. The present invention has accordingly been accomplished. The present invention, therefore, comprises the following inventions.
(1) A method for producing a polymer comprising a (meth)acrylic ester monomer unit as a molecular chain and having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond,
which comprises polymerizing a (meth)acrylic ester monomer using a solvent not containing any aromatic solvents as a polymerization solvent.
(2) The method according to the above paragraph (1),
wherein the polymerization solvent is one or more members selected from the group consisting of alcohol solvents and carbonyl group-containing solvents.
(3) The method according to any of the above paragraphs (1) and (2),
wherein the polymerization solvent is one or more members selected from the group consisting of aliphatic alcohols containing 3 or 4 carbon atoms and dialkyl carbonates.
(4) The method according to any of the above paragraphs (1) to (3),
wherein the (meth)acrylic ester monomer is a mixture of
(1) an alkyl (meth)acrylate monomer containing an alkyl group of 1 to 8 carbon atoms and
(2) an alkyl (meth)acrylate monomer containing an alkyl group containing 10 or more carbon atoms.
(5) A method for producing a polymer comprising a (meth)acrylic ester monomer unit as a molecular chain and having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond,
which comprises polymerizing (meth)acrylic ester monomer using a polymerization solvent of one or more members selected from the group consisting containing aliphatic alcohols containing 3 or 4 carbon atoms and dialkyl carbonates but not containing an aromatic compound in a concentration over 1,000 ppm based on the said polymer.
(6) The method according to any of the above paragraphs (1) to (5),
wherein the polymerization solvent is 2-propyl alcohol.
(7) The method according to any of the above paragraphs (1) to (5),
wherein the polymerization solvent is dimethyl carbonate.
(8) The method according to any of the above paragraphs (1) to (7),
wherein 2,2xe2x80x2-azobis(dimethylvaleronitrile) is used as a polymerization initiator.
(9) A polymer composition comprising
a reactive composition (C) comprising
a polymer (A) comprising a (meth)acrylic ester monomer unit as a molecular chain and having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond and
an oxyalkylene polymer (B) having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond and
a nonaromatic solvent component, with the aromatic solvent content of the polymer composition being not more than 1,000 ppm based on the whole reactive component (C) and
said polymer (A) being obtainable by the method according to any of the above paragraphs (1) to (8).
(10) The composition according to the above paragraph (9)
wherein the total emission of organic compounds from said reactive composition (C) into the air is less than 1,500 xcexcg/m3 
as measured by the method described in the Feb. 14, 2001 edition of GEV Specification and Classification Criteria established by GEV: Gemeinschaft Emissionskontrollierte Verlegewerkstoffe e.V.
(11) The composition according to the above paragraph (9)
wherein the total emission of organic compounds from said component (C) into the air is less than 500 xcexcg/M3 
as measured by the method described in the February 14, 2001 edition of GEV Specification and Classification Criteria established by GEV: Gemeinschaft Emissionskontrollierte Verlegewerkstoffe e.V.
(12) The composition according to any of the above paragraphs (9) to (11),
wherein the oxyalkylene polymer as a starting material for the oxyalkylene polymer (B) having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond is an oxyalkylene polymer
produced by at least one method selected from the group consisting of the anionic polymerization method using a caustic alkali, the chain-extending reaction method starting with an oxyalkylene polymer, the polymerization method using a double metal cyanide complex as a catalyst, the polymerization method using cesium metal as a catalyst, and the polymerization method using a polyphosphazene salt as a catalyst.
(13) The composition according to any of the above paragraphs (9) to (12),
wherein the silicon-containing functional group capable of crosslinking through formation of a siloxane bond in each of said polymer (A) and polymer (B) is at least one member selected from the group consisting of dimethylmonomethoxysilyl, methyldimethoxysilyl, trimethoxysilyl, methyldiethoxysilyl, triethoxysilyl, methyldiisopropenyloxysilyl, and triisopropenyloxysilyl group.
(14) The composition according to any of the above paragraphs (9) to (13),
wherein the oxyalkylene polymer
as a starting material for the oxyalkylene polymer (B) having a silicon-containing functional group capable of crosslinking through formation of a siloxane bond is a polymer
produced by the polymerization method using a double metal cyanide complex as a catalyst and
having a number average molecular weight, Mn, of not less than 6,000 and a molecular weight distribution, Mw/Mn, of not more than 1.6.
(15) The composition according to any of the above paragraphs (9) to (14),
wherein the total emission of organic compounds into the air from the cured artifact
obtainable by allowing the reactive composition (C) to cure at atmospheric temperature for 10 days and further at 50xc2x0 C. for 14 days
is less than 100 xcexcg/m3.
(16) The composition according to any of the above paragraphs (9) to (15),
wherein the reactive component (C) substantially does not contain any of toluene, xylene, styrene, ethylbenzene, p-dichlorobenzene, di-2-ethylhexyl phthalate, di-n-butyl phthalate, and formaldehyde.
(17) The composition according to any of the above paragraphs (9) to (15),
wherein the reactive component (C) is such that the total emission of organic compounds therefrom into the air
as measured by the method described in the Feb. 14, 2001 edition of GEV Specification and Classification Criteria established by GEV: Gemeinschaft Emissionskontrollierte Verlegewerkstoffe e.V.
is less than 1 xcexcg/m3 for any of toluene, xylene, styrene, ethylbenzene, p-dichlorobenzene, di-2-ethylhexyl phthalate, and di-n-butyl phthalate and less than 5 xcexcg/m3 for formaldehyde.